Medicare enrollment periods, decoded.
Medicare doesn’t let you sign up just any time — it runs on specific windows, and missing one can mean a penalty that follows you for life. This page lays out every enrollment period in plain English: when it happens, who it’s for, and exactly what you can do. Then we’ll help you find the one that applies to you.
Initial Enrollment Period (turning 65)
Your Initial Enrollment Period, or IEP, is your first chance to sign up for Medicare. It’s a 7-month window built around your 65th birthday — the three months before your birthday month, your birthday month itself, and the three months after.
If you don’t have other qualifying coverage and you miss your IEP, you may face a lifelong late-enrollment penalty on Part B and Part D — and you may have to wait for a later window to sign up at all. This is the window not to miss.
General Enrollment Period
General Enrollment Period
Didn’t sign up for Part A or Part B when you were first eligible, and don’t qualify for a Special Enrollment Period? This is your yearly chance to enroll.
Medigap Open Enrollment Period
Medigap Open Enrollment
This is the single most valuable window for anyone who wants a Medicare Supplement — and it’s easy to miss. It starts the month you’re both 65 or older and enrolled in Part B, and lasts six months.
Annual Enrollment Period (Fall Open Enrollment)
Annual Enrollment Period
The busy season. Every fall, anyone with Medicare can review and change their Advantage and drug coverage for the year ahead — and it’s the ideal time for a free plan checkup.
Medicare Advantage Open Enrollment
Medicare Advantage Open Enrollment
If you’re already in a Medicare Advantage plan and the new year isn’t working out, this window gives you one more chance to change course.
Special Enrollment Periods
Certain life events open a Special Enrollment Period — a chance to enroll or change coverage outside the normal windows, often without penalty. Here are the most common triggers.
Losing employer coverage
When you or your spouse retire and group health coverage ends, you get a window to enroll in Part B and a plan — usually penalty-free.
Moving
Moving to a new address or outside your plan’s service area opens a window to pick a plan available where you now live.
Changes in other coverage
Losing Medicaid, Extra Help, or other creditable coverage can open a window to make changes.
Your plan changes
If your plan leaves Medicare or stops serving your area, you get a window to choose a new one.
Entering or leaving a facility
Moving into or out of a nursing home or similar institution can qualify you for special timing.
Other situations
Several less-common events also qualify. When in doubt, ask — we’ll tell you if a window is open for you.
Every enrollment period at a glance
All the windows in one place — when each happens, who it’s for, and what you can do.
| Enrollment period | When it happens | Who it’s for | What you can do |
|---|---|---|---|
| Initial Enrollment IEP | 7 months around 65 | Everyone turning 65 | Sign up for Parts A, B, and D; or join a Medicare Advantage plan. |
| General Enrollment GEP | Jan 1 – Mar 31 | Those who missed their IEP | Sign up for Part A and/or Part B. A late penalty may apply. |
| Medigap Open Enrollment | 6 months from Part B at 65 | New Medigap buyers | Buy any supplement with no health questions or higher price. |
| Annual Enrollment AEP / Fall Open | Oct 15 – Dec 7 | Anyone with Medicare | Join, switch, or drop Advantage or Part D for the coming year. |
| Advantage Open Enrollment MA OEP | Jan 1 – Mar 31 | People already in Advantage | Switch Advantage plans or return to Original Medicare + Part D. |
| Special Enrollment SEP | After a qualifying event | People with a life-event trigger | Enroll or change coverage tied to the event, often penalty-free. |
Which period applies to me?
A quick way to point yourself in the right direction. When in doubt, one free call settles it.
I’m turning 65 soon
Your Initial Enrollment Period — the 7-month windowI have (or am leaving) employer coverage
Likely a Special Enrollment Period — often penalty-freeI missed signing up at 65
The General Enrollment Period (Jan 1 – Mar 31)I have Medicare and want to change plans
Fall Annual Enrollment (Oct 15 – Dec 7)Explore next
Not sure which window you’re in? Let’s find out — free.
Tell us your birthday, whether you’re still working, and your current coverage, and we’ll map your exact enrollment dates so you never risk a penalty. No cost, no pressure — just clear timing you can count on.
May River Medicare Insurance is an independent agency and is not affiliated with or endorsed by the U.S. government, the federal Medicare program, or CMS. Enrollment rules and dates are set by Medicare and may change; this page is general education, not individual advice. Guaranteed-issue rights for Medicare Supplements vary by state and situation. For a complete list of your options, contact Medicare.gov or 1-800-MEDICARE.